This invention relates to a "vial-syringe" type medical device. In particular, the invention relates to a disposable prefilled syringe that is ready to be used.
Patent application No. WO-A-93/02728 describes such a conventional device having a tubular body, a nosepiece for a hollow needle, a sliding piston, a protective cover, a protective cap, and inviolability means. The tubular body may be transparent and contains the medicinal liquid that is to be injected in a patient. The nosepiece for the hollow needle communicates with the inside of the tubular body. A sliding piston is provided within the tubular body and is arranged in a predetermined position with respect to the tubular body opposite the nosepiece. The outside extremity of the sliding piston can be actuated by the user, while the inside extremity of the piston forms an internal space with the rest of the tubular body that is partially filled with a dose of the medicinal liquid. The protective cover is coaxial to and placed in a sliding manner on the tubular body and is of sufficient length to completely cover the needle in a protruding position after the injection is performed. The protective cap is positioned in a retractable manner on the front of the tubular body and protects at least the nosepiece of the tubular body. The inviolability means, in particular, is a low resistance, ring-shaped rip line.
A drawback of the above-described device is that it is possible to reuse the syringe by reinserting a new cartridge, which is detrimental in terms of safety and limits the field of application.
Pursuant to U.S. Pat. No. 4,747,837, a similar device is described but has a syringe that is not prefilled and the cap provided inside of the cover at the nosepiece of the body is held by means of friction rather than by inviolability means. This device is also provided with blocking means for the cover in its protruding position impeding any ulterior use. It is possible, however, to move the cover towards the front and to block it inadvertently, thus rendering the device unusable.